A battery which is provided in a vehicle supplies electric power to devices (i.e., electrical loads) such as an air conditioner, lights and the like. A battery of this type is connected to an electric generator which generates electricity using the rotation of an engine which is provided in the vehicle, and can be charged while the engine is running. There exists a vehicle which can supply electric power directly to the aforementioned devices from the electric generator when the electrical load on the battery is large. This electric generator of the vehicle has a high-generation mode in which it generates much electricity and a low-generation mode in which it generates relatively little electricity. These modes are switched between by an electrical control unit for switching. It is known that the switching of generation modes is performed according to the remaining capacity of the battery, a deceleration state of the vehicle, and a volume of electrical load or the like (see, for example, PATENT DOCUMENT 1).
PATENT DOCUMENT 1: Japanese Unexamined Patent Application, First Publication No. H05-137275 (paragraphs [0023] to [0034] and FIG. 6)